Aircraft wheel assemblies typically include a heat shield positioned between the wheel and the discs of a brake assembly located within the wheel. The heat shield is provided to limit conduction and radiation heat transfer from the discs to the wheel assembly, as well as to prevent hot brake material created during braking from being forced outward against the inside of the wheel. Excessive temperatures in the wheel can cause damage and potentially failure of the wheel and/or tire, so the effectiveness and integrity of the heat shield is important. To that end, it is often necessary to perform maintenance on the heat shield in more frequent intervals than the remainder of the wheel and brake assembly. Heat shield maintenance may require replacing the heat shield, or a portion of it, if damaged or degraded during operational use or maintenance operations.
The wheel assembly often includes rotor drive keys, such as conventional beam keys or boss keys, circumferentially spaced around the interior of the wheel and oriented generally parallel to an axis of rotation of the wheel. The drive keys are spaced from the wheel and secured at both ends, and act as engagement and driving members for the rotating discs of the brake assembly. The drive keys may be spaced from the interior of the wheel to reduce conduction heat transfer from the brake to the wheel. In prior art heat shield assemblies, the heat shield may be secured to the drive keys, either directly or indirectly. In this way the heat shield segments are spaced from the wheel, thereby providing an air-filled insulation layer between the heat shield and the wheel. While this method of attachment is effective at limiting heat transfer to the wheel, prior art attachment mechanisms for securing the heat shield to the drive keys present several drawbacks, particularly with respect to routine maintenance of the heat shield.
One prior art approach includes a single piece heat shield secured between the wheel and drive keys. The heat shield is spaced from both the wheel and drive keys to minimize heat transfer between the brake and the wheel. Such a heat shield may be effective at reducing heat transfer to the wheel, but removing a damaged heat shield requires removing all of the drive keys, which results in added time and difficulty, and therefore added maintenance costs.
Other prior art heat shields, such as that disclosed in U.S. Pat. No. 5,002,342, are formed by a plurality of interleaved segments that allow for thermal cycling caused by temperature changes. The segments of the heat shield are individually removable from the wheel, but removal of a heat shield segment requires removal of the drive keys to which it is attached. Other prior art heat shields, such as those disclosed by U.S. Pat. Nos. 5,851,056 and 7,051,845, include heat shield segments disposed between adjacent drive keys and supported by heat shield carriers positioned over and extending the length of the drive keys. The heat shield segments of these heat shield assemblies can be removed individually from the wheel without removing any of the drive keys. However, the heat shield carriers and other supporting and anchoring mechanisms of these systems are complicated and have a relatively large number of parts, and may result in increased manufacturing and maintenance costs.
Thus, there is a need for an improved heat shield assembly that provides easy assembly and removal of heat shield segments.